Compressors of gas turbine engines have alternating rows of rotating blades and stationary vanes. The vanes have vane platforms located adjacent the rotor for the purpose of containing the gas flow. This requires seals to limit air recirculation around the platform. Conventionally these are labyrinth type seals with knife edges on the rotor and an abradable surface on the vane platform. Also, the vane platform segment circumferential thermal growth gaps allow gas path air to bypass around the vanes. Similar seals are required to limit the gas flow bypass as well as between the rotor and vane.
Because of circumferential thermal growth the vane platforms are frequently segmented permitting the growth without a stress buildup. The vanes and platforms are therefore subject to vibration and dampers are required to deter this vibration.
Vane platform and any seal secured thereto has a radial movement which is a function of the expansion of the outer casing to which the vanes are secured, and the expansion of the vanes. The portion of the seal secured to the rotor shaft has a radial expansion which is a function of the temperature and structure of the shaft assembly. Differential radial expansion is experienced which leads to opening up of the conventional labyrinth type seals during certain operating conditions, and the concomitant increased leakage.